1. Field of the Invention
This invention relates to the field of water based epoxy resins. It particularly relates to one component water based epoxy resins which are useful as adhesives.
2. Prior Art
Water based epoxy resins are known in the art. Prior art water based epoxy resins generally utilize an emulsifier and an organic solvent in their formulation. The presence of organic solvent provides the problem of volatile solvent release. Therefore, those skilled in the art have sought to provide a water based epoxy resin which is free of the difficulties of using large amounts of organic solvents. In U.S. Pat. No. 3,998,771 a process is disclosed whereby a carboxylic acid is reacted with a primary amine to form an amide. This amide is then reacted in excess with an epoxy resin and the product water dispersed and further reacted with enough epoxy resin to stoichiometrically cure the resin.
A water reducible coating system is described in U.S. Pat. No. 4,167,498 which is prepared by combining a bisphenol A epoxy resin with a polyamide prepared from fatty acids and an amino propyl derivative of a polyoxyalkylene polyamine.
U.S. Pat. No. 4,308,183 describes a water borne coating employing a bisphenol A epoxy resin produced by addition of an ethoxylated nonylphenol and a long chain organic phosphatide.
U.S. Pat. No. 4,315,044 describes a self-emulsifying epoxy resin employing the diglycidyl ether of bisphenol A, bisphenol A and the diglycidyl ehter of polyoxyalkylene glycol in aqueous medium.
Many other patents describe water reduced epoxy adhesive systems. The use of a polyoxyalkyleneamine to modify the epoxy resin and solubilize it in aqueous medium is heretofore unknown in the art.
It is well known in the art that there is a need for a water reduced adhesive which minimizes the use of hazardous or polluting solvents while producing a bond of considerable strength.